Planta Med 2007; 73 - P_536
DOI: 10.1055/s-2007-987316

Evaluating CYP3A4 inhibitory activity of Echinacea extracts using NMR and multivariate data analysis

M Modarai 1, N Wilson 1, M Politi 1, A Suter 2, A Kortenkamp 1, M Heinrich 1
  • 1The School of Pharmacy, University of London, 29/39 Brunswick Square, London WC1N 1AX United Kingdom
  • 2Bioforce AG, 9325 Roggwil, Switzerland

Previously we have shown that commercially available echinacea extracts vary widely in their inhibitory activity on CYP3A4 (IC50 values: 12.71µg/ml -1812µg/ml) in the supersome assay1. Modern NMR-spectroscopy and principal component analysis allows evaluation of differences between complex mixtures2. To correlate such differences to CYP3A4 inhibition we examined various Echinacea extracts. Six commercially available Echinacea extracts were chosen. Each extract was separated into ethanolic and water fractions, which were assayed for CYP3A4 inhibition. In tandem, 400MHz 1H- NMR spectra were obtained in deuterated ethanol or deuterium oxide with internal standards. Principal component analysis was conducted on the data.

The inhibitory activity of the extracts resided mostly in the ethanolic fraction (with IC50 values ten folds lower than original extract e.g. Echinaforce IC50: 22µg/ml, vs. ethanolic fraction 2µg/ml). 1H NMR spectra of the ethanolic fractions showed a clear difference between the most and least active extracts. Greater inhibition was associated with the presence of peaks at 1–3 ppm and 6–8 ppm (visual inspection).

Principal component analysis revealed good correlation between differences in 1H spectra and IC50 values. Key contributors were identified in the regions: 0.875 ppm, 0.925 ppm, 1.275 ppm, 1.325 ppm. The ethanolic fraction of Echinaforce was further fractionated by SPE (C-18, water: ethanol 10% step gradient). Two potent fractions were identified (IC50: 0.43–0.58µg/ml). 1H NMR analysis also revealed additional peaks at ˜7ppm, which were unique to these fractions. Amongst other compounds, we suspect that the ethanol soluble alkylamides, (potent CYP3A4 inhibitors) may be found in these fractions.

Acknowledgements: Bioforce for funding this project.

References: [1] Modarai, M. et al. (2007) Journal of Pharmacy and Pharmacology 59: 567–573 [2] Holmes, E. et al. (2006) Planta Med. 72: 771–785.